According to the Chicago Sun-Times, the NFL says that
legalized Internet gambling would represent a threat to the "integrity
of our game". A spokesman for the NFL, Brian McCarthy, has gone
on record to say that if the UIGEA is overturned, there would be more
illegal gambling on professional football games. (Gambling on the games
is already a huge, multi-billion dollar industry.)

"We understand that illegal gambling currently occurs, but there is
little we can do about that," McCarthy said in the article. "However,
we can exercise our right to oppose Internet betting on our games. ...
Gambling on our games -- online or off line -- threatens the integrity
of our games and all the values they represent."

This activity by the NFL to keep the UIGEA in place pits it squarely
against the PPA, whose chairman, Al D'Amato, has made some strong
statements against those who try to censor online activity. "How dare
you come into my house and tell me what I can and can't do on the
Internet!" D'Amato said in the Sun-Times article.

The article also states that other sports organizations, like the NCAA and
the leagues for professional baseball, basketball, and hockey, are also
fighting the UIGEA. But the NFL has been the most vocal on the topic,
and has spent the most time and money trying to win over Congress.

To provide some historical context, it isn’t just Internet gambling
that the NFL fears. The league has opposed gambling all the way back to
1960.